Are there any ergonomic tips for screenwriters?

You need to check your setup. Feet on the floor, arms at a comfortable 90-or-so degrees. I strongly believe in arm rests, but different things work for different people. Your typing surface probably needs to be a lot lower than you think. My desk lowers to just two inches above my knees. Everyone has different opinions on chairs. I’ve found the expensive ones aren’t necessarily better. Try a bunch.

You need to change your keyboard. I use this one, which rightfully scares people, but I find works great. You may need to try a bunch of different ergonomic keyboards before you find one that works.

You need to take breaks. A lot of them. Walk around. You’ll actually get more done if you’re not staring at the screen the whole time.

Like crutches, gloves can help, but they’re not fixing the problem. These Handeze support gloves saved my life, but I’m happy not to need them now.